Fish communicate through behavior and appearance, and changes are usually responding to something in their environment. This section covers the questions aquarium owners ask when something doesn't look right — from hiding to surface-gasping to not eating — with the water chemistry context that makes everything else make sense.
Previously active fish that suddenly disappear behind rocks or plants are usually responding to something. Water quality, temperature, and aggression are the top three things to check.
Fish gasping at the surface is almost always an oxygen or water quality problem. It's a distress signal that needs prompt attention.
A fish refusing food can be something simple — wrong food type, acclimation period — or a sign of illness or poor water quality. Here's how to tell.